Hi Maia,
I did try that – unfortunately when I tested flattening the sequence after edits were finished, Premiere didn’t recognize the audio as being linked to the video and only flattened the video, leaving the audio in a limbo state where it marked it as still being part of a multicam sequence and refused to flatten. It did this whether I copy-pasted just the video from the simplified sequence into the multicam, or both the audio and video from the simplified sequence into the multicam.
Sadly it looks like the only option in my particular case is to keep moving the media down onto the bottom tracks manually.
Thanks for trying though!